The On the Border restaurant at Broadway and the south loop remained shut down Tuesday afternoon following a kitchen fire earlier in the day.
Firefighters were called to the restaurant a few minutes before 10:00am after kitchen workers noticed the fire in a hood ventilation system above one of the grills and manually triggered a chemical fire suppression system built into the hood and its supporting duct-work.
Deputy Fire Marshal Tony Gumber said that ventilation system was undergoing routine maintenance prior to the fire breaking out.
"There were people here that were here to work on that system but it was routine maintenance," he said. "They weren't here because they had had a problem."
Gumber said investigators discovered that part of the maintenance work involved the temporary deactivation of a large fan on the roof of the restaurant that would drive airflow within the ducts and keep temperatures at an appropriate level.
It was unclear why an electrical relay switch in the system failed to properly re-activate the fan when employees began cooking prior to their lunch service.
Ultimately, without the fan running, Gumber said the temperature rose to the point that the "grease-laden" duct-work ignited.
Firefighters continued to check the restaurant for flare-ups throughout Tuesday afternoon. No customers were inside the restaurant at the time of the fire, and no one was injured.